Greece's main stock market fell up to 11 percent on the news, while the country's 10-year bond yields spiked above 9 percent. Ahead of the vote, the euro slipped to a near-28-month low against the dollar.

Samaras said he was confident of a victory in the forthcoming elections, Reuters reported, although his party is trailing behind the opposition Syriza party in opinion polls.

'Major threat'

If Greece's popular anti-austerity Syriza party is elected in January, there are fears that the country's international bailout could be put in jeopardy.

The party has promised to scrap Greece's tough austerity policies if it gets into power. The unpopular cost-cutting measures are a condition of the country's bailouts —worth 240 billion euro ($296 billion)—implemented by the International Monetary Fund, European Central Bank and European Commission.

Although Greece is nearing the end of its aid program, the country still needs to implement further austerity measures in order to receive the last tranche of aid from lenders – something that could be jeopardized by a Syriza win.

"Investors are concerned that... it is highly likely that anti-austerity party will become the ruler of the country and this will be a major threat for the country's remarkable progress which is running a current account surplus now," chief market analyst at Ava Trade, Naeem Aslam, said Monday.

Although Greece looks to be on track for a primary budget surplus in 2014, the country is battling with public debt of 175.5 percent of gross domestic product (GDP), according to the European Commission. It also has an unemployment rate of around 26 percent, which rises to around 50 percent for young people.

'Grexit' fears revived

There are also fears that if Syriza comes into power, Greece could even leave the 18-country euro zone—something that Nick Hungerford, director and chief executive of investment management service Nutmeg, said would be "devastating" for the country.

"The moment they left, they would have to devalue any currency they had very quickly. Their sovereign rating would presumably fall to less-than junk, and you'd have real of trouble getting any (investment) going in the country," Hungerford told CNBC Monday.

However, one analyst noted that Syriza would not be guaranteed an easy victory in January's election, despite its 3.5-percentage-point lead over Samaras' New Democracy party in an opinion poll on December 23.

"As for the likely outcome of early parliamentary elections, Syriza is expected to win them. However, it will probably do so with a small margin and not enough parliamentary seats to form a government on its own, given that it would need to secure at least 36-38 percent of the votes to control an outright majority in parliament," Wolfango Piccoli, managing director of risk consultancy Teneo Intelligence, said in a note Sunday.